1. Field of the Invention
The invention relates to an automatically locking belt roll-up device for safety belts, especially for motor vehicles, having a belt shaft rotatably supported in a roll-up device housing, a rewinding spring connected to the belt shaft, ratchet teeth fixedly attached to the belt shaft, and a spring-loaded pawl which automatically locks with the ratchet teeth by the force of the spring after the belt is put on.
2. Description of the Prior Art
In known designs of this type (German Published Prosecuted Applications DE-AS No. 12 49 704 and DE-AS No. 14 31 257), a belt shaft is supported in bearings in a strong roll-up device housing and can turn, for unwinding a belt fastened on the belt shaft, against the force of a rewind spring. Locking discs with ratchet teeth which cooperate with a pawl are arranged on both sides of the belt winding. Functionally connected to the belt shaft is a cam which can rotate a predetermined angle and which can be moved into one position for unwinding and into the other position for rewinding. The pawl is pushed in the direction of the belt winding by a spring. If the belt is wound up completely, the pawl is pushed outward through contact with the outer belt layer, i.e., away from the ratchet teeth. While the pawl could drop into the ratchet teeth after a predetermined length of the belt is unwound, it is initially held outside the locking position by the adjusted cam, so that putting-on the belt is not inhibited. The cam is reset only after brief rewinding of the applied belt and then the pawl drops into the ratchet teeth under the force of the spring, so that further unwinding of the belt is no longer possible. It is a disadvantage of this known design that interference with putting on the belt occurs if the belt pullout is stopped or the belt is run backward briefly, because as explained immediately above, the belt shaft is brought into the locking position. Pulling the belt out further, which is necessary for putting the belt on completely, is possible only if the belt is rewound completely, so that the roll-up device is again in its starting position, i.e., the cam again holds the pawl away from the ratchet teeth.